'Save Excalibur' fails: Madrid euthanizes Ebola patient's dog

The dog was sedated before being euthanized, according to health authorities. Its body was moved, following protocol, to a place where it could be cremated.

Excalibur's death comes despite a public push, including a Change.org petition signed by about 400,000 people.

"It would be much easier to isolate or quarantine the dog just as they have the victim's husband," the petition stated, rather than forcing Romero and her husband to lose "one of the family."

Romero is a nurse's assistant at Madrid's Carlos III hospital, where she is believed to have gotten Ebola while caring for missionaries being treated for the virus there. She is in isolation at the same hospital. Her husband is also there under observation, though he hasn't shown any symptoms of Ebola.

Hospital worker with Ebola 'doing better'

Health authorities put down Excalibur because of concern it may have become infected with Ebola.

That raised questions: Can dogs really get Ebola and spread it to humans? What about other animals?

In Africa, Ebola infection "has been documented through the handling of infected chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines," WHO says, though researchers think fruit bats are what they call the virus' "natural host."

Studies on dogs transmitting the infection are not as conclusive. During the 2001-2002 Ebola outbreak in Gabon, scientists from the U.S. Centers for Disease Control and Prevention found signs of the virus in around 25% of dogs living in the affected area of the country. Yet none of the animals became symptomatic or died of the disease during the study period.

"The only conclusion that may be safely drawn from this study is that the animals encountered Ebola virus (and their immune systems responded)," Margaret H. Gilbert, a clinical veterinarian and assistant professor of medicine at Tulane National Primate Research Center, wrote in an email to CNN. "Whether or not dogs shed Ebola once their immune systems encounter it remains to be seen."

When other wild animals like chimpanzees are infected with the virus, "the infection is highly lethal and causes huge outbreaks and massive population declines," the scientists wrote in their published paper.

How did Spanish nurse catch Ebola?

Dogs may excrete infectious Ebola particles in their urine, feces or drool, the scientists wrote, as has been observed with other animals.

"Asymptomatically infected dogs could be a potential source of human Ebola outbreaks," they wrote.